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## org.bouncycastle.crypto.generators
Class KDFCounterBytesGenerator

    java.lang.Object
      org.bouncycastle.crypto.generators.KDFCounterBytesGenerator

All Implemented Interfaces:
  DerivationFunction, MacDerivationFunction

public class KDFCounterBytesGenerator
extends java.lang.Object
implements MacDerivationFunction

This KDF has been defined by the publicly available NIST SP 800-108 specification. NIST SP800-108 allows for alternative orderings of the input fields, meaning that the input can be formated in multiple ways. There are 3 supported formats: - Below [i]_2 is a counter of r-bits length concatenated to the fixedInputData. 1: K(i) := PRF( KI, [i]_2 || Label || 0x00 || Context || [L]_2 ) with the counter at the very beginning of the fixedInputData (The default implementation has this format) 2: K(i) := PRF( KI, Label || 0x00 || Context || [L]_2 || [i]_2 ) with the counter at the very end of the fixedInputData 3a: K(i) := PRF( KI, Label || 0x00 || [i]_2 || Context || [L]_2 ) OR: 3b: K(i) := PRF( KI, Label || 0x00 || [i]_2 || [L]_2 || Context ) OR: 3c: K(i) := PRF( KI, Label || [i]_2 || 0x00 || Context || [L]_2 ) etc[] with the counter somewhere in the 'middle' of the fixedInputData. This function must be called with the following KDFCounterParameters(): KI The part of the fixedInputData that comes BEFORE the counter OR null the part of the fixedInputData that comes AFTER the counter OR null the length of the counter in bits (not bytes) Resulting function calls assuming an 8 bit counter. 1. KDFCounterParameters(ki, null, "Label || 0x00 || Context || [L]_2]", 8); 2. KDFCounterParameters(ki, "Label || 0x00 || Context || [L]_2]", null, 8); 3a. KDFCounterParameters(ki, "Label || 0x00", "Context || [L]_2]", 8); 3b. KDFCounterParameters(ki, "Label || 0x00", "[L]_2] || Context", 8); 3c. KDFCounterParameters(ki, "Label", "0x00 || Context || [L]_2]", 8);

Constructor Summary
`KDFCounterBytesGenerator(Mac prf)`

Method Summary
`int` | `generateBytes(byte[] out, int outOff, int len)`
`Mac` | `getMac()` return the MAC used as the basis for the function
`void` | `init(DerivationParameters param)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### KDFCounterBytesGenerator

    public KDFCounterBytesGenerator(Mac prf)

Method Detail

### init

    public void init(DerivationParameters param)

  Specified by:
    `init` in interface `DerivationFunction`

### getMac

    public Mac getMac()

  Description copied from interface: `MacDerivationFunction`
  return the MAC used as the basis for the function

  Specified by:
    `getMac` in interface `MacDerivationFunction`
  Returns:
    the Mac.

### generateBytes

    public int generateBytes(byte[] out,
                             int outOff,
                             int len)
                      throws DataLengthException,
                             java.lang.IllegalArgumentException

  Specified by:
    `generateBytes` in interface `DerivationFunction`
  Throws:
    `DataLengthException`
    `java.lang.IllegalArgumentException`

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